1. Field of the Invention
The present invention relates to an ink jet printing head provided in an ink jet printing apparatus for ejecting liquid (e.g., ink) to perform a printing operation. In particular, the present invention relates to a printing element substrate provided in the ink jet printing head and the manufacture method thereof.
2. Description of the Related Art
Conventional printing head 1000 shown in FIG. 15 includes: a printing element unit H1002; and an ink supply unit H1003. The printing element unit H1002 includes: a first printing element substrate H1101, a second printing element substrate H1100, a printing element substrate supporting plate H1200, an electric wiring substrate H1300, an electric contact substrate H2200, and an electric wiring member supporting plate H1400 or the like. The ink supply unit H1003 includes: an ink supply member H1500, a flow path formation member H1600, a joint seal member H2300, a filter H1700, and a seal rubber H1800, or the like. The printing element substrate supporting plate H1200 includes one ink supply path through which the ink is applied to the first printing element substrate H1101 and plurality of ink supply paths through which the ink is applied to the second printing element substrate H1100. Each of these ink paths extend along a direction along which the plurality of ink ejecting orifices formed in each of the printing element substrates H1100 and H1101 is arranged.
The printing element substrates of printing head H1000 is assembled thorough steps as described below. First, an electric wiring member supporting plate H1400 is fixedly adhered to a printing element substrate supporting plate H1200 and a first printing element substrate H1101 and a second printing element substrate H1100 are fixed to the printing element substrate supporting plate H1200 by electric wiring substrate adhesive agent. Then, electric wiring substrate adhesive agent for fixedly adhering a back face of the electric wiring substrate supporting plate H1400 is applied on the electric wiring substrate supporting plate H1400 to fixedly adhere an electric wiring substrate H1300.
As shown in FIG. 16, the above printing head H1000 is attached to a tank holder H2000 that retains an ink tank in a detachable manner, and thereby a cartridge is formed that is provided in a carriage of an ink eject printing apparatus in a detachable manner.
By the way, current ink jet printing apparatuses have another important objective of providing a low-cost ink jet printing head in addition to providing the high quality color printing equal to or higher than that by silver halide photography with a high speed. Means for achieving this objective include the printing element substrate supporting plate H1200 and the electric wiring substrate supporting plate H1400 made of resin. The current printing element substrate supporting plate H1200 and electric wiring substrate supporting plate H1400 are formed by subjecting alumina (Al2O3) material to a press working and a cutting work. This causes high cost plates to cause higher cost of the resultant ink jet printing head. Thus, a resin-made printing element substrate supporting member has been tried in which the printing element substrate supporting plate H1200 is integrated with the electric wiring substrate supporting plate H1400.
The resin-made printing element substrate supporting member can be manufactured by an injection molding. Thus, the time required for the manufacture can be reduced, providing advantages of the contribution to a low-cost ink jet printing head and a higher design freedom of the shape of the member. However, resin material used for a printing element supporting member has a higher linear expansion coefficient than that of alumina. Thus, a risk is caused where a defect may be caused by the manufacture or other heating environment. For example, in the above-described assembly step of the printing head H1000, the sealant of an electric joint section cures when being heated. Thus, the sealant cures while causing the printing element substrate supporting member to have a higher temperature. Furthermore, the printing element substrate supporting member also has a different temperature due to heat generated from a printing element substrate during the operation of the ink jet printing apparatus or a change in the environment in which the ink jet printing apparatus is operated. Thus, when the printing element substrate supporting member has a high linear expansion coefficient, the deformation amount of the printing element substrate supporting member more is increased, causing a possibility where the printing element substrate may be peeled from the printing element substrate supporting member or the printing element substrate itself is destroyed.
In order to solve the problems as described above, a conventional approach has used resin material for forming a printing element substrate supporting member that includes filler with a higher rate than that of generally commercially available resin material.
However, the high speed printing by ink jet printing apparatuses in recent years causes a trend of a further increasing number of ejecting orifices to cause a proportional increase in the size of a printing element substrate in a direction along which the ejecting orifices are arranged. Thus, further reduction of a linear expansion coefficient of resin material has been required. Resin material including filler with a higher rate tends to have a smaller linear expansion coefficient. However, resin used for a printing element substrate supporting member already includes filler in a higher amount than that of filler included in generally commercially available resin material. Thus, an increase in the amount of filler included in such resin is limited in consideration of molding conditions. Thus, it has been required to reduce the linear expansion coefficient of printing element substrate supporting sections in the printing element substrate supporting member without changing an inclusion rate of filler included in the resin material. The linear expansion coefficient of the printing element substrate can be reduced by uniforming an orientation direction of the filler included in resin material. The filler orientation directions tend to be oriented to a direction along which the resin material flows. In an injection molding of the printing element supporting plate H1200, the resin material which forms areas between the ink supplying paths for supplying color ink flows along the direction along which the ink supply paths extend. According to the flowing of the resin material, the filler included in the resin material in the area tends to be oriented along the direction along which the ink supplying paths extend. As a result, the linear expansion coefficient of the resin material in the areas between the ink supplying paths become relatively lower than that of an areas other than the areas between the ink supplying paths. However, resin flowing direction in areas near ends of the ink supplying paths is not uniformed, and thereby orientation direction of filler included in the resin in the area near the ends of the ink supplying paths is not uniformed. As a result, the linear expansion coefficient of resin in the area near the ends of the ink supplying paths for supplying color ink becomes relatively lower than that of the other area. Further, in the area around the one ink supplying path for supplying black ink, the orientation direction of the filler included in the resin tends not to be uniformed. Accordingly, the linear expansion coefficient of resin in the area near the one ink supplying path becomes relatively higher. It is therefore required to provide the printing element supporting substrate in which filler orientation direction in the printing element supporting section in the printing element substrate is uniformed.